1. Field of the Invention
This invention relates to a temperature-sensitive fluid type fan coupling apparatus which, in an automobile engine, for example, enables the rotation of a cooling fan to be controlled in compliance with change of temperature in the neighborhood of the engine thereby incessantly effecting automatic regulation of the volume of cooling air supplied to the engine in compliance with the travelling condition of the automobile.
2. Description of the Prior Art
The conventional fluid type fan coupling apparatus of the kind under discussion, as illustrated in FIG. 2, comprises a rotary shaft member (21) made of an iron material as a driving side component, a tightly sealed housing (22) supported as a following side component through the medium of a bearing (24) on the rotary shaft member (21) and provided on the external part thereof with a cooling fan. A partition plate (30) having of an oil flow adjusting hole (32) is adapted to divide the interior of the tightly sealed housing into an oil reservoir (31) and a torque transmission chamber (27). A driving disc (28) is disposed in the torque transmission chamber (27) and secured at the leading end of the rotary shaft member (21) in a state retaining a torque transmission gap (27') in conjunction with the opposed inner peripheral surface of the tightly sealed housing (22). A valve member (34) is disposed inside the oil reservoir (31) and adapted to open and close the flow adjusting hole (32) in compliance with the change of shape which a temperature-sensitive member (33) disposed on the front side of the tightly sealed housing (22) undergoes owing to the change of temperature of the ambience thereof. A dam (35) and an oil circulation route (36) are both disposed in part of the inner peripheral surface of the tightly sealed housing (22) opposed to the outer peripheral surface of the driving disc (28) destined to collect oil thereon during the rotation thereof, which circulation route (36) is connected to the dam (35) and adapted to start from the torque transmission gap (27') and terminate in the oil reservoir (31) side.
In the conventional fan coupling apparatus constructed as described above, however, since the tightly sealed housing (22) having the cooling fan attached thereto is formed as a following side component, molded inevitably in the form of a thick-walled cast part of aluminum alloy material contrary to the demand for products of reduced weight, and fabricated as provided on the outer surface thereof with a multiplicity of radially disposed upright radiation fins, it generally assumes an increased weight, adds to the inertial moment exerted to the apparatus, inevitably necessitates use of a large bearing on account of an increase in the load exerted on the bearing (24), and rather tends to increase the overall weight of the apparatus as a finished product. Further, the heat generated by the shear of oil in the torque transmission gap (27') is conducted to the tightly sealed housing (22) made of an aluminum alloy of high thermal conductivity and consequently deforms the fitting part of resin on the fan side. Moreover, since the temperature-sensitive member (33) is directly attached to the front side of the tightly sealed housing (22) made of an aluminum alloy in close proximity to the oil reservoir (31) and, consequently, the course for heat conduction is short, the temperature-sensitive member (33) is susceptible of the influence of the propagation of heat through the oil inside the oil reservoir and liable to induce errors in the change of shape due to change of temperature in the ambience and admit hysteresis in the control characteristics.